package core_kernel

The timing-wheel implementation uses an array of "levels", where level i is an array of length 2^b_i, where the b_i are the "level bits" specified via Level_bits.create_exn [b_0, b_1; ...].

A timing wheel can handle approximately 2 ** num_bits t intervals/keys beyond the current minimum time/key, where num_bits t = b_0 + b_1 + ....

One can use a Level_bits.t to trade off run time and space usage of a timing wheel. For a fixed num_bits, as the number of levels increases, the length of the levels decreases and the timing wheel uses less space, but the constant factor for the running time of add and increase_min_allowed_key increases.

max_num_bits is how many bits in a key the timing wheel can use, i.e. 61. We subtract 3 for the bits in the word that we won't use:

• for the tag bit
• for negative numbers
• so we can do arithmetic around the bound without worrying about overflow

In create_exn bits, it is an error if any of the b_i in bits has b_i <= 0, or if the sum of the b_i in bits is greater than max_num_bits. With ~extend_to_max_num_bits:true, the resulting t is extended with sufficient b_i = 1 so that num_bits t = max_num_bits.

default returns the default value of level_bits used by Timing_wheel.create and Timing_wheel.Priority_queue.create.

default = [11; 10; 10; 10; 10; 10]

This default uses 61 bits, i.e. max_num_bits, and less than 10k words of memory.

num_bits t is the sum of the b_i in t.